ioloop.py 文件源码

def _run_callback(self, callback):
        """Runs a callback with error handling.

        For use in subclasses.
        """
        try:
            ret = callback()
            if ret is not None and is_future(ret):
                # Functions that return Futures typically swallow all
                # exceptions and store them in the Future.  If a Future
                # makes it out to the IOLoop, ensure its exception (if any)
                # gets logged too.
                self.add_future(ret, lambda f: f.result())
        except Exception:
            self.handle_callback_exception(callback)